Glossary

Each InnoDB page (usually 16kb in size) contains a log sequence number, or LSN. The LSN is the system version number for the entire database. Each page’s LSN shows how recently it was changed.

innodb_file_per_table

By default, all InnoDB tables and indexes are stored in the system tablespace on one file. This option causes the server to create one tablespace file per table. To enable it, set it on your configuration file,

[mysqld]innodb_file_per_table

or start the server with --innodb_file_per_table.

innodb_expand_import

This feature of Percona Server implements the ability to import arbitrary .ibd files exported using the Percona XtraBackup--export option.

The size in bytes of the memory buffer to cache data and indexes of InnoDB‘s tables. This aims to reduce disk access to provide better performance. By default:

[mysqld]innodb_buffer_pool_size=8MB

InnoDB

Storage engine which provides ACID-compliant transactions and foreign key support, among others improvements over MyISAM. It is the default engine for MySQL as of the 5.5 series.

MyISAM

Previous default storage engine for MySQL for versions prior to 5.5. It doesn’t fully support transactions but in some scenarios may be faster than InnoDB. Each table is stored on disk in 3 files: .frm, .MYD, .MYI

XtraDB

Percona XtraDB is an enhanced version of the InnoDB storage engine, designed to better scale on modern hardware, and including a variety of other features useful in high performance environments. It is fully backwards compatible, and so can be used as a drop-in replacement for standard InnoDB. More information here .

my.cnf

This file refers to the database server’s main configuration file. Most linux distributions place it as /etc/mysql/my.cnf, but the location and name depends on the particular installation. Note that this is not the only way of configuring the server, some systems does not have one even and rely on the command options to start the server and its defaults values.

datadir

The directory in which the database server stores its databases. Most Linux distribution use /var/lib/mysql by default.

xbcrypt

To support encryption and decryption of the backups, a new tool xbcrypt was introduced to Percona XtraBackup. This utility has been modeled after The xbstream binary to perform encryption and decryption outside of Percona XtraBackup.

xbstream

To support simultaneous compression and streaming, a new custom streaming format called xbstream was introduced to Percona XtraBackup in addition to the TAR format.

ibdata

Default prefix for tablespace files, e.g. ibdata1 is a 10MB autoextensible file that MySQL creates for the shared tablespace by default.

.frm

For each table, the server will create a file with the .frm extension containing the table definition (for all storage engines).

.ibd

On a multiple tablespace setup (innodb_file_per_table enabled), MySQL will store each newly created table on a file with a .ibd extension.

.MYD

Each MyISAM table has .MYD (MYData) file which contains the data on it.

.MYI

Each MyISAM table has .MYI (MYIndex) file which contains the table’s indexes.

.exp

Files with the .exp extension are created by Percona XtraBackup per each InnoDB tablespace when the xtrabckup --export option is used on prepare. These files can be used to import those tablespaces on Percona Server 5.5 or lower versions, see restoring individual tables“

.MRG

Each table using the MERGE storage engine, besides of a .frm file, will have .MRG file containing the names of the MyISAM tables associated with it.

.TRG

File containing the Triggers associated to a table, e.g. :file:`mytable.TRG. With the .TRN file, they represent all the Trigger definitions.

.TRN

File containing the Triggers’ Names associated to a table, e.g. :file:`mytable.TRN. With the .TRG file, they represent all the Trigger definitions.

.ARM

Each table with the Archive Storage Engine has .ARM file which contains the metadata of it.

.ARZ

Each table with the Archive Storage Engine has .ARZ file which contains the data of it.

.CSM

Each table with the CSV Storage Engine has .CSM file which contains the metadata of it.

.CSV

Each table with the CSV Storage engine has .CSV file which contains the data of it (which is a standard Comma Separated Value file).

.opt

MySQL stores options of a database (like charset) in a file with a .opt extension in the database directory.

.par

Each partitioned table has .par file which contains metadata about the partitions.